Field of the Invention
The present invention relates generally to propellant gas actuated semi-automatic and full automatic firearms that have a bolt carrier and bolt assembly being energized by propellant gas pressure for linear movement during firing activity. The present invention also concerns a gas key component of a propellant handling system of a firearm that is mounted to the bolt carrier by retainer screws and defines a gas supply passage that is in communication with a gas port of the bolt carrier. More specifically, the present invention concerns propellant flow and pressure control and adjustment by selective positioning of a gas pressure and flow adjustment member having at least a portion thereof that is adjustably positioned within a gas supply passage of the propellant gas handling system of a firearm.
Description of the Prior Art
It is known that various changes in propellant gas actuated firearms, such as semi-automatic and automatic tactical rifles, such as the ammunition being used or the use of suppressors and other devices, significantly influence the shooting and auto cycling characteristics of such firearms. For example, the addition of a flash and noise suppressor to the barrel of a propellant gas energized rifle will change the propellant gas pressure, flow and dwell time acting on the auto-cycling mechanism and can cause the firearm to fail to function properly. Changes in the pressure, volume or timing of propellant gas entering the gas actuation chamber of the bolt carrier and bolt group of gas energized rifles, such as M-16 and AR-15 rifles, potentially alter the ammunition handling and shooting, i.e., auto-cycling characteristics of the rifles. Various types of apparatus changes have been made in propellant gas energized firearms to adjust the propellant gas handling systems, i.e., auto-cycling mechanisms of such firearms. Most of the apparatus changes have been provided in or about the gas block, which is a gas handling structure that is mounted externally of the barrel of a gas energized rifle. The gas block has internal gas passages that are in communication with a gas port that extends through the barrel structure and intersects the barrel bore enabling a portion the propellant gas within the bore of the barrel to be employed to actuate the auto-cycling mechanism of the rifle.
Tactical rifles, such as the military tactical rifles M-16 and M-4, and their semi-automatic equivalent, the AR-15 rifle, each have a bolt carrier group including a bolt carrier and bolt member that cycle within the upper receiver of the firearm by propellant gas pressure that is generated by combustion of gunpowder upon cartridge firing. The bolt carrier defines a bolt chamber within which a rear portion of a bolt member is positioned for linear and rotational movement. The bolt member is provided with gas seal rings which establish movable sealing with an internal seal surface of the bolt chamber. A space between an internal wall of the bolt carrier and the rear end portion of the bolt member constitutes a gas actuation chamber that received propellant gas via a gas supply passage system that extends to the upper receiver from the gas block member.
The bolt carrier member is linearly moveable rearwardly by the force of propellant gas pressure within the gas actuation chamber and the bolt member is urged forwardly within the bolt chamber and within the upper receiver of the firearm mechanism by propellant gas pressure acting on the bolt carrier surface and the gas seal rings of the bolt member when the firearm is discharged. As the bolt carrier is moved rearwardly by propellant gas pressure acting on it and on the bolt member, the bolt carrier further loads a buffer spring which drives the bolt carrier and its bolt forwardly when the propellant gas pressure has dissipated sufficiently that it is overcome by the spring force of the buffer system. During initial propellant gas energized rearward retraction movement of the bolt carrier the bolt member is rotated sufficiently to unlock its bolt head from a locking receptacle. The bolt member is then retracted along with the bolt carrier and during such retraction movement extracts a spent cartridge case from the cartridge chamber of the barrel and ejects the spent cartridge case through a cartridge port of the upper receiver. As the bolt carrier and bolt member are driven forwardly by the force of the buffer spring, the bolt head picks up a fresh cartridge from a magazine and feeds it into the cartridge chamber of the barrel in readiness for firing.
The propellant gas for energizing the bolt carrier and bolt group is conducted from the gas port of the barrel of the firearm, through a gas tube and through a gas supply passage of a gas key member and into the bolt chamber of the bolt carrier where it acts to move the bolt carrier and bolt member in opposite directions. The bolt carrier member defines a wall structure having a gas supply port and defines a generally planar gas key mounting surface that is intersected by the gas supply port. A gas key, also having rear or terminal end having a generally planar surface is secured to the planar surface of the bolt carrier by retainer screws and defines a gas supply passage that is in communication with the gas supply port.
Gas pressure control adjustment features have been provided to permit the user of the firearm to adjust the pressure and volume of propellant gas that is permitted to be propagated from the gas port through a gas supply tube to the gas supply passage of the upper receiver of the rifle. U.S. Pat. Nos. 8,345,626, 8,443,712 and 8,850,951 are representative of adjustable gas block apparatus for control of the propellant volume and pressure being conducted to the bolt carrier and bolt group of an auto-cycle mechanism for a firearm.
Typically, these gas adjustment features have been provided in the region of the gas block of the rifle as taught by U.S. Pat. No. 8,973,483 of Sullivan. U.S. Pat. No. 8,393,259 of Mark C. LaRue shows a gas block having a gas passage selector mechanism and being mounted to a rifle barrel having multiple gas ports to permit selective control of the characteristics of propellant gas entering the gas tube from the barrel bore. Variable gas block passage dimensions are shown to be provided in U.S. Pat. No. 8,960,069 of Soong et al by employment of a sliding regulator plate of a gas block. U.S. Pat. No. 8,950,313 of Kenney discloses a propellant gas regulator system that is provided in a gas block that receives propellant gas via two gas ports of a rifle barrel. U.S. Pat. No. 8,807,011 of Langevin illustrates the provision of another type of gas pressure adjustment mechanism for the gas block of a propellant gas energized rifle.
A related invention involving a gas key mounted to a bolt carrier seat is set forth in U.S. Pat. No. 8,991,295 of Mark C. LaRue. A port seal member is provided at the gas flow port of the bolt carrier and eliminates the leakage problems that often occur with surface-to-surface sealing of a typical gas key member. The port seal member serves to prevent any propellant gas leakage at the planar interface of the bolt carrier and gas key member, and thus effectively prevents depletion or decrease of the gas pressure that enters the bolt chamber of the bolt carrier and thus ensures against any decrease of the propellant gas actuating pressure that acts on the seal areas of the bolt member and bolt carrier member.
As mentioned above, propellant gas pressure, volume and timing characteristics is employed to cycle a bolt carrier and bolt group to move the bolt carrier member within the upper receiver against the force of a buffer and buffer spring assembly that is present within the gun stock mechanism. This propellant gas actuated cycling activity also drives the bolt member forwardly within the bolt chamber of the bolt carrier, thus moving the bolt head into the bolt locking receptacle of the barrel. During the terminal portion of the bolt closing movement the bolt member is rotated by a cam pin that extends through a cam slot of the bolt carrier and is engaged within a cam pin receptacle of the bolt member. During relative bolt carrier and bolt movement the cam pin reacts within the cam slot and causes rotation of the bolt member, causing the bolt head to establish locking engagement within the bolt locking receptacle. Unlocking rotation of the bolt member is caused by the cam pin and cam pin receptacle as the bolt carrier causes retraction movement of the bolt member.
When suppressors or other devices are mounted to the threaded muzzle end of a firearm barrel the propellant gas pressure within the bore of the barrel rather than being instantaneously vented at the muzzle of the barrel. Within a suppressor the propellant gas pressure is gradually diminished as the propellant gas enters and is processed within the multiple internal chambers or cavities within the suppressor body. Moreover, the propellant gas is reflected and agitated as it progresses serially through the suppressor to the multiple discharge openings, thus slowing the gas discharge and preventing the loud sharp noise that occurs when a suppressor is not employed. A suppressor or a different type of ammunition changes the pressure pulse characteristics within the bore of the firearm barrel and thus changes the characteristics of the propellant gas pulse that is employed for operation of the auto-cycling mechanism of the firearm. Thus, it is desirable to provide such firearms with the capability for simple and efficient adjustment of the propellant gas pulse to achieve propellant gas variations that can be coordinated with such changes.